Te igitur, clementissime Pater.
Latin text
Te igitur, clementissime Pater, per Jesum Christum Filium tuum Dominum nostrum, supplices rogamus ac petimus, uti accepta habeas et benedicas haec dona, haec munera, haec sancta sacrificia illibata.
Context
The Roman Canon begins in sacred quiet with the Church asking the Father to accept the sacrifice.
Source: Missale Romanum 1962, Ordo Missae, as published by Divinum Officium.
Divinum Officium